This invention relates to a method and apparatus for the physical separation and recovery of a highly enriched fraction of aleurone cell particles from commercial wheat bran, in which a fraction of aleurone cell particles and pericarp-testa particles obtained by hammer-milling of wheat bran is subjected to size-clasification/particle electrification/particle electrostatic fractionation treatments, whereby highly purified aleurone cell particles are obtained.
Wheat bran is the outer layer of the wheat caryopsis and is itself composed of layers of different cell types. The outer layers of the bran arise from the parent plant and are the seed-coat or pericarp-testa. The inner layer is the aleurone, which is the outer-most layer of the endosperm. The aleurone cells, which comprises more than half the weight of wheat bran, are thick-walled and enclose the cell contents, which are rich in protein of high nutritional value and B-vitamins.
Aleurone cells are important constituents in animal feed-stuffs and a source of dietary fibre in human nutrition. Aleurone particles thus constitute a potentially useful commodity as a relatively cheap source of "dietary fibre" and are of a particular commercial interest on that account due to the current emphasis on "dietary fibre" in nutrition.
Methods for the preparation of large amounts of aleurone particles are therefore of actual or potential commercial significance in the food industry, however; known methods lack efficiency.
In the conventional roller milling of whole wheat grain, the bran (pericarp-testa and aleurone) together with some adhering starchy endosperm is collected in the bran and pollard streams. Separation and recovery of aleurone particles from the bran by known methods has been unsatisfactory.
A method for the fractionation of aleurone cell particles from pericarp-testa, devised by Steven D. J., is published in J. Sci. Food Agric. (1973) 24, 307-317. This procedure is based on a density gradient separation in benzene-carbon tetrachloride and is limited by the capacity of the gradient and the availability of high capacity centrifuges. Its success is highly temperature dependent.